/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/MeshOpPreviewHelpers.h
Configure the Standard and In-Progress materials
void ConfigureMaterials ( [TArray](API\Runtime\Core\Containers\TArray)< [UMaterialInterface](API\Runtime\Engine\Materials\UMaterialInterface) * > StandardMaterials, [UMaterialInterface](API\Runtime\Engine\Materials\UMaterialInterface) * InProgressMaterial, [UMaterialInterface](API\Runtime\Engine\Materials\UMaterialInterface) * SecondaryMaterial )